Pathologists use several techniques in determining a lymphoma diagnosis. General histology is studied first with tissues samples from a biopsy that have been fixed in formalin, embedded in paraffin and then sectioned using a micotome. These samples are then viewed under a microscope where general morphology is observed. Morphologic diagnosis was discussed on the pathology page. Because there are so many subtypes of lymphoma, phenotyping and karyotyping techniques must be employed to make an accurate diagnosis. Following are those most commonly used techniques in lymphoid cancer diagnosis:
Immunohistochemistry (IHC):
- Start with unstained samples of tissue that have been fixed in formalin, embedded in wax and sliced on a microtome.
- Stain the sample sections with antibodies marked with a chromagen (marker) in order to decorate the surface or inside of the cells.
- A number of different stains will be completed to test for various markers: CD20, CD3, CD30, BCL2, Cyclin D1, etc.
- A cell that stains positive for a certain marker will indicate what type of cell it is: B-cell or T-cell.
- The positive staining will also help determine the expression of the lymphoma (phenotype) based on where the cells are showing up. For example, cells that stain positive for CD30 around the outside of the cell and show up in the cell’s golgi bodies are indicative of anaplastic large-cell lymphoma, a type of NHL (seen below).
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CD30- APLCL. Click on image to enlarge
lymphoma 